re
I haven't heard of an LSD for a syncro front diff - just locking front
diffs,
>> solid shaft instead of VC, etc.>
> A viscous coupling IS an LSD, just using fluid mechanics instead of
> solid. Its locking ratio can be altered by changing the fluid
> viscosity.

those two statements suggest that you see the VC as a limit slip for the
front differential.
If so, ,
I belive you are incorrect there buddy.

The VC is not a differential between the two front axles.
it is a 'limited slip or grab device"  between front and  rear axles and
differentials.

people get nutty when I say the VC is a front-rear 'differential' as it's
not a differential in the usual sense ........like ones in a front or rear
diffs that provides and controls distribution to the axles on either side of
whichever diff.

but it does allow 'slip' when needed, front to rear, and gives 'grab' when
needed.

In AWD cars there is need for some sort of give or slip or differentiaing in
3 places, rear, front, and front-to-rear.
that is because, on pavement, when a car goes around a corner, all four
wheels travel a different distance.

this is why you feel binding on a 4WD ( not AWD ) vehicle on pavement when
it's in 4WD - there's no give or slip front to rear.
True AWD vehciels need 'some slip, and grab when desired' front to rear ,
which the VC does.

 the VC has nothing to do with controling the axles of the front diff.
It would need to have a locker there, or an LSD - otherwise a syncro front
differential is a normal 'open' differential.
scott

----- Original Message -----
From: "Andrew Grebneff" <goose1047@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Sunday, December 20, 2009 11:25 AM
Subject: Re: report on Limited Slip Differential

>> I havn't heard of an LSD for a syncro front diff - just locking front
>> diffs,
>> solid shaft instead of VC, etc.
>
>
> A viscous coupling IS an LSD, just using fluid mechanics instead of
> solid. Its locking ratio can be altered by changing the fluid
> viscosity.
>
> My Porsche trans is LSD... can't wait to try it out, if I ever get a
> van on the road.
>
> BUT beware... with an LSD you can still get stuck... just more stuck
> than without!
>
> --
> Regards
> Andrew Grebneff
> Dunedin
> New Zealand
> Fossil preparator
> Mollusc, Toyota & VW van fan